Method of stabilizing polymeric organic compositions with 3&#39;,5&#39;-dibromo-2&#39;-hydroxyacetophenone

ABSTRACT

THE PREPARATION OF 3&#39;&#39;,5&#39;&#39;-DIBROMO-2&#39;&#39;-HYDROXYACETOPHENONE AND ITS USE AS AN ILTRAVIOLET LIGHT ABSORBER AND AS A FIRE RETARDANT FOR POLYMERIC AND ORGANIC COATING COMPOSITION ARE DESCRIBED.

United States Patent 3,719,509 METHOD OF STABILIZING POLYMERIC ORGANIC(JOMPOSITIONS WITH 3',5 DIBROMO 2-HY- DROXYACETOPHENONE Stanley J.Buckman and John D. Pet-a, Memphis, Tenn., assignors to BuckrnanLaboratories, Inc., Memphis, Tenn. No Drawing. Filed Jan. 4, 1971, Ser.No. 103,815 Int. Cl. C09d 5/14, 5/16; C09k 3/28 U.S. Cl. 106-15 FP 18Claims ABSTRACT or m nrsctosunn The preparation of3',5'-dibromo-2'-hydroxyacetophenone and its use as an ultraviolet lightabsorber and as a fire retardant for polymeric and organic coatingcompositions are described.

This invention relates to a method whereby the resistance of polymericorganic materials and polymeric organic coating compositions,hereinafter called polymeric organic compositions, to the deterioratingeffects of ultraviolet light and to fire are increased. Moreparticularly, the foregoing objectives are accomplished by incorporatinginto the polymeric organic compositions the compound 3 ',5'-dibromo-2-hydroxyacetophenone.

It is Well known that many organic compositions such as polymericorganic compositions tend to undergo deterioration when exposed toultraviolet light. Light in the ultraviolet portion of the spectrum andparticularly that having a wavelength within 290-400 millimicrons causesphotocatalyzed changes, such as yellowing and/or embrittlement ofunstabilized polymeric compositions. These changes are obviouslyundesirable and this is particularly true when the composition isinitially colorless, transparent, or translucent and is to be usedsubsequently under conditions that will subject it to long exposure tosunlight or other sources of ultraviolet light radiation. Examples ofsuch applications include translucent roofing materials, transparentstructures, decorative structures, decorative and protective coatings,and impact-resistant windows.

In recent years, many organic compounds have become available which canabsorb ultraviolet light and convert it to less harmful forms of energysuch as heat, vibrational energy, or less harmful radiation. Theseorganic stabilizers, in addition to absorbing ultraviolet radiation inthe selected range for the polymeric compositions being treated, must becompatible therewith, have little or no initial color, be reasonablyinexpensive, be chemically stable, and have a low toxicity, especiallyfor stabilizing compositions to be used subsequently in the foodindustry.

A good ultraviolet absorber for use in polymeric organic compositionsshould absorb the ultraviolet radiation in daylight, impart no or verylittle color to the composition, should be sutficiently stable towithstand curing conditions, and should absorb ultraviolet lightsufficiently to protect the composition against yellowing anddecomposition on exposure to ultraviolet light. The compound must havesufficient solubility in various types of materials so that it may beincorporated therein, it should be capable of withstanding leachingaction of solvents or loss by exudation.

Generally, an effective ultraviolet absorber should have its peakabsorption above a wavelength of 300 millimicrons or the absorption peakmay be at a higher wavelength as long as the absorption drops offsufficiently as it approaches the visual range so that no color isvisible. In addition, to be effective it should show a high degree ofabsorbancy in the desired wavelength range, especially at thosewavelengths sufficiently below the visual range so that the compound hasno yellow color.

Although, as pointed out above, many compounds have been suggested forthe stabilization of polymeric organic compositions againstdeterioration caused by ultraviolet light, none have been entirelysatisfactory as all have been deficient in one or more qualities whichthe ideal ultraviolet absorber must possess. These include, in additionto lack of color, the ability to become firmly incorporated in thecomposition to be stabilized and the ability to absorb ultraviolet lightover a wide range. The

latter is important because individual polymeric organic.

compositions are generally most susceptible to deterioration byradiation of a specific wavelength. For example, polyethylene,polypropylene, and polystyrene are susceptible to radiation wavelengthsof 300-320 millimicrons. Many of the absorbers disclosed in the priorart exhibit excellent ultraviolet light absorption only over a verylimited wavelength. Another criteria of a polymeric organic compositionin addition to its resistance to deterioration on exposure toultraviolet light is that it be as resistant to fire as possible.

Heretofore when it was necessary to protect polymeric organiccompositions against deterioration caused by exposure to ultravioletlight and to impart fire-retardant properties to the composition, theuse of two additives was mandatory; one to protect the compositionagainst ultraviolet light and the other to attain the desiredfireretardant properties. This is objectionable because when twoadditives are used, each must not only perform its particular functioneffectively, but, in addition, the two must be compatible. Obviously, asingle compound effective both as an ultraviolet light absorber and as atireretardant would eliminate completely the compatibility requirementand for that reason be desirable.

It is, therefore, a principal object of the present invention to providean additive for polymeric organic compositions which is effective as anultraviolet light absorber and is capable of rendering such compositionsfireretardant.

It is another object of our invention to provide a composition which isresistant to degradation by ultraviolet light radiation and is fireresistant.

These and other objects and advantages will become apparent as thedescription proceeds.

To the accomplishment of the foregoing and related ends, this inventionthen comprises the features hereinafter fully described and particularlypointed out in the claims, the following description setting forth indetail certain illustrative embodiments of the invention, these beingindicative, however, of but a few of the various ways in which theprinciples of the invention may be employed.

In brief, the foregoing objects and advantages are attained byincorporating into a polymeric organic composition susceptible todeterioration by the action of ultraviolet light radiation and fire thecompound 3,5'-dibromo-2'-hydroxyacetophenone in an amount varying fromabout 0.5 percent to about 15 percent or more by weight based on thetotal weight of the polymeric organic composition. We have found thatthis compound because of its outstanding ultraviolet light absorbingproperties over a Wide range of wavelengths combined with its ability toimpart fire-retardant properties to the finished product make it anideal additive for polymeric organic compositions.

Polymeric organic compositions which can be protected from the degradingeffects of ultraviolet light and/or fire by the use of3,S'-dibromo-2-hydroxyacetophenone include alkyd resins as disclosed inUS. Pats. 1,847,783, 1,860,164, 1,950,468, and 2,087,852; epoxy resinsas disclosed in US. Pat. 2,886,473; polyester resins;

polyurethane; polyethylene; polypropylene; polystyrene; polyvinylchloride resins; cellulosic and acrylic polymers; linear super polyamideobtained by condensing an aliphatic polyethylenediamine with adicarboxylic acid; industrial coatings including decorative andprotective coatings wherein one or more of the components thereofcomprises an organic composition suscetpible to deterioration whenexposed to ultraviolet light or heat; coated fabrics such as fabricscoated with polyvinyl chloride and polyolefin; and polyvinylidenechloride monofilaments.

In order to disclose the nature of the invention still more clearly, thefollowing illustrative examples will be given. It is understood,however, that the invention is not to be limited to the specificconditions ,or details.

set forth in these examples, except insofar as such limitations arespecified in the appended claims.

In the examples, parts where used are parts by weight.

EXAMPLE 1 Preparation of 3,5-dibromo-2'-hydroxyacetophenone Brominesubstitution of 2'-hydroxyacetophenone may occur on the benzene ring,the aliphatic side chain, or both, depending upon the specificexperimental conditions followed. Heretofore if the desired result wassubstitution on the ring, the reaction was conducted by adding bromineto a solution of 2-hydroxyacetophenone whereby the desired product wasobtained in about a 55 to 70 percent yield. Suitable solutions for usein this reaction have been restricted to glacial acetic acid and analkali-metal acetate, acetic acid and water, ethanol and water, andisopropanol and water.

We have now unexpectedly found that 3',5-dibromo- 2'-hydroxyacetophenonecan be obtained in almost quantitative yields by the bromination of anaqueous suspension of 2'-hydroxyacetophenone at a temperature rangewhich may vary from about 25 to about 100 C., but preferably from about50 to about 60 C., for a period of time varying from about 1 to about 30hours.

In this example, two runs were made:

Run No. 1: A 5-liter, four-necked, round-bottom reaction flask equippedwith a stirrer, thermometer, condenser, and dropping funnel was chargedwith 544.6 grams (4 moles) of 2-hydroxyacetophenone and 2,400 grams ofwater and the temperature raised to 50-60 C. Bromine was added slowlybeneath the surface of the liquid for a period of 3 hours While thetemperature was maintained at 5060 C. A total of 671 grams (8.4 moles)of bromine was added. The product precipitated as a pale yellow solidduring the bromine addition. After the bromine addition was completed,the reaction mixture was stirred for 30 minutes and then heated atreflux (105 C.) for minutes. The crude reaction product melted andsettled to the bottom of the flask when the agitator was stopped. Thislower layer quickly solidified when the reaction mixture was cooled andthe water layer containing hydrogen bromide formed during the reactionwas removed by decantation.

Two liters of water was added to the reaction flask and the mixture washeated and agitated at reflux for 10 minutes. The agitator was stoppedand the mixture cooled. The product, which again settled to the bottomof the flask as a liquid layer and crystallized, was obtained bydecanting the water layer. The product layer was melted and poured intoa Pyrex dish to cool. This treatment removed residual water and thecrude paleyellow product was obtained in essentially a quantitativeyield and had a melting point of 100-105 C.

Recrystallization of the crude product from isopropanol gave3,5'-dibromo-2-hydroxyacetophenone as pale yellow needles with a meltingpoint of 108-110 C. The ultraviolet spectrum showed a very strongabsorption maximum at 347 millimicrons.

Run No. 2: A 100-gallon, glass-lined reaction vessel equipped with aheating jacket and agitator was charged with 110 pounds (0.81 poundmole) of 2-hydroxyacetophenone and 485 pounds of water and thetemperature raised to 55 C. Bromine vapor obtained by boiling liquidbromine in a separate glass container was passed into the reactor abovethe liquid level at a constant rate for 25 hours while the temperaturewas maintained between 50 and 60 C. A total of 265 pounds (1.66 poundmoles) of bromine was added. After the bromine addition was completed,the reaction mixture was agitated for 30 minutes and then heated at C.for 30 minutes. A small amount of excess bromine and about 15 pounds ofwater were removed from the reaction mixture. The agitator was thenstopped and the liquified product was removed through a valve at thebottom of the. reactor.

The water-hydrogen bromide solution left in the reactor was removed andthe reactor was rinsed and charged with 480 pounds of water. The Waterwas heated to 100 C. and the crude product, which had solidified, wasadded to the hot water. The reactor was sealed and heated to C. for 15minutes. The product was again removed from the bottom of the reactor asa liquid which quickly soldified to a pale yellow crystalline solid witha melting point of IDS-107 C. The total yield was 240 pounds of3,5'-dibromo-2'-hydroxyacetophenone.

EXAMPLE 2 Plasticized polyvinyl chloride In this example, the effect ofvarious amounts of 3',5'- dibromo-2'-hydroxyacetophenone on aplasticized polyvinyl chloride film was determined. Five such filmsamples were prepared by dry blending at 88 C. as follows:

Sample No. 1 contained 1.0 part barium stearate, 1.0 part cadmiumstearate, 60 parts dioctyl phthalate, and 100 parts polyvinyl chloride.The dry-blended material was fused at 175 C. for 5 minutes. The fusedmass was chopped and the resulting granules were pressed into a sheet atC. with a Carver press.

Samples Nos. 2, 3, 4, and 5 were prepared by the same procedure asSample No. 1 except that 1.0, 2.0, 5.0, and 10.0 parts of3',5'-dibromo-2'-hydroxyacetophenone was added to each sample,respectively, before blending.

Sheets of approximately 25 and 60 mils thickness were made.

The 25-mil thick films were used to determine the eifectiveness of theacetophenone derivative in ultraviolet light absorption by exposure in achamber with a combination of ultraviolet light and daylight fromfluorescent tubes. Each sample was exposed so that the film protected aportion of a light-colored maple tongue blade. After 240 hours exposure,the wood exposed directly to the light and the wood exposed behind thefilm of Sample No. 1 showed considerable darkening. In contrast, thewood protected by those fihns containing 1.0, 2.0, 5.0, and 10.0 partsof 3,5'-dibromo-2'-hydroxyacetophenone showed no darkening.

Film Samples Nos. 4 and 5 containing 5.0 and 10.0 parts of3',5'-dibromo-2'-hydroxyacetophenone showed considerably less curlingand exuding of the plasticizer than those samples containing lesserquantities of the acetophenone.

The five film samples were used to evaluate fire resistance imparted bythe acetophenone derivative. Due to their flexibility, the 0.5 x 5 inchsamples were hung vertically and ignited for 15 seconds with a Bunsenburner in a vented hood. Although all samples were self-extinguishing onremoval of the Bunsen burner, the duration of the flame varied inverselywith the acetophenone content.

EXAMPLE 3 Fiber glass-reinforced polyester 3',5'-dibromo-2'-Tris(dibromopropyl) hydroxyacetophenone: phosphate 1.0 6.0

The ratio of fiber glass to polyester resin was approximately 1 to 3 byweight. The samples were formed on glass between two sheets ofcellophane separated by a 3-millimeter glass rod, and heat cured at 80C. for 20 minutes.

Samples were cut into 0.5 x 4.5 inch pieces and tested for fireresistance in a procedure similar to that in ASTM 635-63. By recordingthe time in seconds required for the flame to be extinguished or for theflame to burn to the 4-inch mark, the flame resistance offered by theproduct at various concentrations is determined. Increasing theconcentration of the product in the plastic resulted in shorter flametime. The use of 2 parts or more of the product converted the plasticfrom a burning material to a self-extinguishing material. The timerequired for self-extinguishing to occur or for 4 inches of sample toburn varied from an average of 210 seconds for the control plastic (0.0part of the brominated acetophenone) to 32 seconds for the plastic with5.0 parts of the acetophenone to 1 second for the plastic with 3 partsof the acetophenone and 6 parts of tris(dibromopropyl)phosphate. Aspecial sample containing 6 parts of tn's(dibromopropyl)phosphate burnedan average of 3.6 seconds.

The effect of ultraviolet light on each of the plastic samples wasdetermined by placing samples in a chamber with ultraviolet light anddaylight from fluorescent tubes. After 100 hours exposure, all sampleswere discolored, although those samples containing the acetophenoneshowed less coloration. The amount of coloration varied inversely as theamount of the acetophenone derivative increased.

'EXAMPLE 4 Clear varnishes In this example,3,5'-dibromo-2'-hydroxyacetophenone was added to each of three differentclear coating compositions of 50 percent solids identified as follows:Medium soya alkyd resin, air-drying polyurethane resin, and a tung oilvarnish at concentrations of 0.0, 0.5, and 1.0 percent by weight basedon the total weight of the clear coating. These coatings were applied tomaple wood surfaces. Two coats were applied allowing 24 hours betweencoats for drying. After the second coat had dried, a portion was cutfrom each of the maple specimens and retained in the dark. The remainingportion of each specimen was exposed in a chamber lighted withultraviolet light and daylight from fluorescent tubes.

After 48 hours exposure, the color of the exposed surface was comparedto that retained in a darkened area. All samples of varnish coatingscontaining 1.0 percent of the acetophenone derivative were lessdiscolored than those containing lesser quantities.

6 EXAMPLE 5 Polypropylene resin In this example, the effect of variousamounts of 3',5'- dibromo-2'-hydroxyacetophenone on a polypropylene filmwas determined. Five such films were prepared as follows:

Sample No. l, which contained parts unstabilized polypropylene, 0.1 partdilauryl thiodipropionate, and 1.0 part of a hindered phenol was fusedin a Plasti-Corder blender at 175 C. for 5 minutes. The hindered phenolused was a product available under the trademark Irganox 1076, which isan alkyl ester of a carboxylic acid containing an alkylhydroxy phenylgroup. This product is further identified in US. Pat. 3,330,859. Thefused material was chopped and the resulting granules pressed intosheets about 25 and 60 mils thick using a Carver press at about C.

Samples Nos. 2, 3, 4, and 5 were prepared by the same procedure asSample No. 1 except that 1.0, 2.0, 5.0, and 10.0 parts of3',5-dibromo-2-hydroxyacetophenone was added to each sample,respectively, before fusion.

The 25-mil thick films were used to determine the efiectiveness of theacetophenone derivative as an ultraviolet light absorber by exposing thefive films in chambers lighted with ultraviolet light and daylightfluorescent tubes for 10 days. At the end of this period, there was lesscrazing and embrittlement of the samples with increasing quantities ofthe acetopheuone derivative used.

The 60-mil thick film samples were evaluated for fire resistanceaccording to ASTM D 635. The time required for the sample to burn 4inches increased directly with the amount of the acetophenone derivativepresent in the sample.

EXAMPLE 6 Polyethylene resin In this example, the effect of variousamounts of 3',5'- dibromo-2'-hydroxyacetophenone on a polyethylene filmwas determined. Five such films were prepared as follows:

Sample No. 1 was prepared by fusing 100 parts of polyethylene in aPlasti-Corder blender at C. for 5 minutes. The fused material waschopped and the resulting granules pressed into sheets about 25 and 60mils thick using a Carver press at about 165 C.

Samples Nos. 2, 3, 4, and 5 were prepared by the same procedure asSample No. 1 except that 1.0, 2.0, 5.0, and 10.0 parts of3',5'-dibromo-2-hydroxyacetophenone were added to each sample,respectively, before fusion.

The 25-mil thick films were tested by exposure in a chamber lighted withultraviolet light and daylight fluorescent tubes. After 4 days exposure,those films containing the acetophenone derivative showed lessembrittlement than the control film. The film samples containingincreasing amounts of the additive showed progressively increasedresistance to embrittlement.

The 60-mil thick film samples were tested for fire resistance bymeasuring the time required to burn 4 inches of the film which was 0.5inch wide. Our results demonstrated that the greater the amount ofacetophenone derivative present in the film, the greater the timerequired.

EXAMPLE 7 Similar beneficial results were obtained when 3',5-dibromo 2'hydroxyacetophenone was incorporated into epoxy resins, polyurethane,polystyrene, and cellulosic and acrylic polymers in the amounts andfollowing the procedure as disclosed in Example 2.

While particular embodiments of the invention have been described, itwill be understood, of course, that the invention is not limited theretosince many modifications may be made, and it is, therefore, contemplatedto cover by the appended claims any such modifications as fall withinthe true spirit and scope of the invention.

The invention having thus been described, what is claimed and desired tobe secured by Letters Patent is:

1. A method of stabilizing a polymeric organic composition susceptibleto degradation by ultraviolet light and fire when exposed thereto, whichcomprises adding to said polymeric organic composition the compound3',5'- dibromo-2'-hydroxyacetophenone in an amount sufiicient tostabilize said polymeric organic composition against ultraviolet lightand fire.

2. The method of claim 1 wherein the polymeric ganic composition ispolyvinyl chloride.

3. The method of claim 1 wherein the polymeric ganic composition ispolyethylene.

4. The method of claim 1 wherein the polymeric ganic composition ispolypropylene.

5. The method of claim 1 wherein the polymeric ganic composition ispolystyrene.

6. The method of claim 1 wherein the polymeric ganic composition is anepoxy resin.

7. The method of claim 1 wherein the polymeric ganic composition is acellulosic polymer.

8. The method of claim 1 wherein the polymeric ganic composition is anacrylic polymer.

9. The method of claim 1 wherein the polymeric ganic composition is apolyvinylidene chloride.

10. The method of claim 1 wherein the polymeric organic composition ispolyvinyl acetate.

11. The method of claim 1 wherein the polymeric organic composition is apolyvinylethylene acetate.

12. The method of claim 1 wherein the polymeric Organic composition is apolyvinyl acrylate.

13. The method of claim 1 wherein the polymeric organic composition is astyrene-butadiene copolymer.

14. The method of claim 1 wherein the polymeric organic composition is astyrenated-vinyl-acrylic terpolymer.

15. The method of claim 1 wherein the polymeric organic composition isan acrylic-butadiene-styrene terpolymer.

16. The method of claim 1 wherein the polymeric organic composition is apolymerized drying oil.

17. The method of claim 1 wherein the polymeric organic composition is apolymerized linseed oil.

18. The method of claim 1 wherein the polymeric organic composition is apolymerized tung oil.

References Cited UNITED STATES PATENTS 2,116,104 5/1938 Dohrn et al.260-592 2,876,210 3/1959 Wynn et al. 260-4595 2,976,259 3/1961 Hardy etal 26045.95

3,000,853 9/1961 Havens 260-45.95

3,192,179 6/1965 Spatz et al. 260-45.95

FOREIGN PATENTS 943,937 12/1963 Great Britain 26045.75

JOAN B. EVANS, Primary Examiner U.S. Cl. X.R.

